Weird voltage out put

[Ground_zero298]

Noticed yesterday my voltage output was at 12.8 on the dash Verified by 3 other components in the truck. That’s at a stop or under throttle, any throttle. Now when the foots off the pedal and she’s coasting it shoots up to 14.8 which is where it’s normally at.

Upon inspection I noticed my onboard charger wasn’t working correctly either. Verified this with another charger.

unhooked the on board and today we have 13.8 volts when stopped or pedal touched, 14.8 on a coast.

any ideas on what I should be looking at for this? Alternator, bms, voltage reg? Makes no sense it jumps up on a coast. Least not to me. ,

charger was hooked up on the other side of the bms and not the neg post direct. Thinking it may have something to do with this.

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[Boreal]

Normal behaviour.

It’s a “smart” charging system.

I would assume that the voltage jumps on coast because while driving the Fuelpumps, Injectors, Spark Plugs and other electronics are under duty. When you lift, there is no load as everything is coasting with you (to some degree)

 

[Brian_B]

Mine does the same thing. I always figured it was something along the lines of what @Boreal described, since it follows with coasting / engine braking.

It hasn’t cooked or drained any batteries on me yet so I figure it’s probably up doing what it’s supposed to do

 

[Ground_zero298]

Thanks for the replies. Mines never behaved like that before. She was sitting in a lift for 2 months. I’ve babied it since putting it back together. It was doing it again when I left yoga today. I finally stood on it and red lined it. Now it’s holding at 14.5 with no fluctuation like before.
So if it’s normal I’ve never seen it fluctuate on mine before. Redlining it I’m assuming corroded connection or loose ground? Not sure. Will monitor and report.

 

[67BroncoG1]

I would venture to say it is smart charging at work except that I had a similar thing happen with my 2016 full size Range Rover and it ended up being a battery that had an intermittent fault.

I used my battery tester on it at it would test out fine yet every so often it would throw a charging system fault. At the suggestions of the blokes on the Rover forums I replaced the battery anyway and the charging returned to normal. Believe it or not that is the only issue I have had with that car in 80,000 miles of ownership.

Frankly, I wish that "smart charging" would just go away. My '67 bronco just charges at 14.2 volts and I never need to worry about it.

 

[Ford Motor Company]

Noticed yesterday my voltage output was at 12.8 on the dash Verified by 3 other components in the truck. That’s at a stop or under throttle, any throttle. Now when the foots off the pedal and she’s coasting it shoots up to 14.8 which is where it’s normally at.

Upon inspection I noticed my onboard charger wasn’t working correctly either. Verified this with another charger.

unhooked the on board and today we have 13.8 volts when stopped or pedal touched, 14.8 on a coast.

any ideas on what I should be looking at for this? Alternator, bms, voltage reg? Makes no sense it jumps up on a coast. Least not to me. ,

charger was hooked up on the other side of the bms and not the neg post direct. Thinking it may have something to do with this.

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